In conventional tobacco drying procedures, cut tobacco is positioned in a rotating heated drum and air is passed through the drum to remove moisture. The drum is mounted with its axis extending a few degrees above horizontal, so that the tobacco passes under the influence of gravity from the higher end to the lower end as the drum rotates about its axis and the tobacco tumbles in the flowing air stream. A typical arrangement is described in U.S. Pat. No. 3,372,488.
The tobacco which is dried in this way has various particle sizes and is dried to an average moisture content. Upon examination of the individual particles resulting from such prior art drying process, it has been found that smaller tobacco particles contain much less than the average moisture content of the tobacco while larger tobacco particles contain more than the average moisture content of the tobacco.
The significantly less moisture content of the small particles renders them brittle and subject to abnormal breakage as they tumble in the drier, thereby impairing their filling power, so that overall, the filling power of the tobacco is impaired by the conventional drying procedure.
This problem is particularly acute when drying shredded stem material produced by the process described in U.S. patent application Ser. No. 244,083 filed Mar. 16, 1981, now U.S. Pat. No. 4,386,617, in the names of Warren A. Backmann et al and assigned to the assignee herein, because the product contains a significantly higher proportion of fine strands than in conventional shredded lamina material.
The aforesaid U.S. patent application describes the shredding of tobacco stem material by thoroughly soaking the stems in water to a moisture content of about 30 to about 60 wt%, fiberizing the soaked stems between counter-rotating ribbed discs spaced apart about 0.05 to about 0.30 inches, and subsequently drying the shredded stem material to a moisture content of about 10 to about 16 wt%. The disclosure of U.S. Ser. No. 244,083, now U.S. Pat. No. 4,386,617, is incorporated herein by reference.